1. Field of the Invention
The present invention relates to an image processing apparatus and control method thereof and, more particularly, to an image processing apparatus which converts input image signals into output image signals represented as a combination of the colored colorant amounts and colorless colorant amounts, and a control method thereof.
2. Description of the Related Art
With recent advances in printing techniques, attention has been paid to improving the image quality dependent on graininess and glossiness in addition to reproduction of tint. In particular, gloss nonuniformity is one factor which greatly degrades the image quality, so a technique for suppressing gloss nonuniformity is needed. As the technique of suppressing gloss nonuniformity, the gloss within an image is made uniform using both colored and colorless colorants. For example, Japanese Patent No. 3591534 proposes a method of controlling the colorless colorant amount based on the type of print medium or the colored colorant amount used. According to this method, when a glossy print medium is used, the colorless colorant amount in a region where no colored colorant is applied is set larger than that in a region where the colored colorant is applied. This suppresses gloss nonuniformity within an image.
However, the simultaneous use of colored and colorless colorants poses the following problem.
It is generally known that when colored and colorless colorants are used at the same time, the reproduced color density becomes lower than the original density of the colored colorant. Particularly when a wide area such as the background has a dark color such as black, degradation of the image quality due to a decrease in the color density stands out.